Image forming apparatus and method for image forming

ABSTRACT

An image forming apparatus including an image forming device, a sensor, and a processor. The image forming device is to form an image on recording medium. The sensor is to irradiate light to the recording medium and detect an amount of light transmitted through the recording medium and an amount of light reflected from the recording medium at each of a plurality of positions. The processor is to determine a thickness of the recording medium based on the amount of light transmitted through the recording medium and the amount of light reflected from the recording medium at each of the plurality of positions. The processor is to then control the image forming device on the basis of the determined thickness.

This application is a continuation application of International PatentApplication No.: PCT/KR2017/006291, filed Jun. 16, 2017, which claimsthe benefit of Japanese Patent Application No.: 2016-211369, filed Oct.28, 2016, in the Japanese Intellectual Property Office, and thedisclosure of which is incorporated by reference herein in its entirety.

BACKGROUND

An image forming apparatus refers to an apparatus that prints print datagenerated by a printing control terminal device such as a computer on arecording paper. Examples of such an image forming apparatus include acopier, a printer, a facsimile, or a multifunction peripheral (MFP) thatcombines functions of the copier, the printer, and the facsimile througha single device.

Generally, such an image forming apparatus performs a printing operationusing a plurality of types of recording medium. Thus, the image formingapparatus has printing conditions such as a conveyance speed, a transfercondition and a fixing condition suitable for various kinds of printingpaper and performs printing by changing the printing conditionsaccording to types of printing paper.

In the image forming apparatus, it is necessary to determine or set thetypes of printing paper in advance to perform printing under appropriateprinting conditions. To determine such printing paper, a technique fordetermining the types of printing paper using data output from anoptical sensor has commonly been used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a brief configuration of an imageforming apparatus according to an example of the disclosure;

FIG. 2 is a block diagram illustrating a configuration of an imageforming apparatus according to an example of the disclosure;

FIG. 3 is a view illustrating a configuration of an image forming partof FIG. 1 according to an example;

FIG. 4 is a schematic view illustrating a brief configuration forexplaining an arrangement of a sensor part of FIG. 1;

FIG. 5 is a conceptual view for explaining an operation of a papersensor of the disclosure;

FIG. 6 is a view illustrating an example of a table relating toconveyance path width calibration coefficients (Km);

FIG. 7 is a view illustrating an example of a table relating to initialcalibration coefficients (Ka);

FIG. 8 is a flowchart illustrating an operation for forming an image inthe disclosure;

FIG. 9 is a graph illustrating a correlation between a weight and theamount of transmitted light of printing paper;

FIG. 10 is a graph illustrating a correlation between a weight and theamount of transmitted light of the printing paper;

FIG. 11 is a table illustrating results of detecting the amount oftransmitted light, the amount of regular reflected light, and the amountof diffused reflected light regarding each of normal smoothness sheetmaterials (A and B) and high smoothness sheet materials (C and D);

FIG. 12 is a graph illustrating a correlation between a thicknesscoefficient K_(thickness) and a thickness of printing paper;

FIG. 13 is a graph comparing a correlation between a weight and theamount of transmitted light of printing paper when the amount of emittedlight from a light emitting source is changed;

FIG. 14 is a graph illustrating a change in the amount of transmittedlight when the amount of emitted light from a light emitting source ischanged and stability of the amount of normalized transmitted light;

FIG. 15 is a conceptual view illustrating another example of a papersensor according to the disclosure; and

FIG. 16 is a flowchart illustrating an image forming method according toan example of the disclosure.

DETAILED DESCRIPTION

Hereinafter, various examples will be described in detail with referenceto the accompanying drawings. The examples described below may bemodified to be implemented in various different forms. In order to moreclearly describe the features of the examples, a detailed description ofmatters known to those skilled in the art will be omitted.

In the disclosure, when it is described that an element is “coupled” toanother element, the element may be “directly coupled” to the otherelement or “coupled” to the other element through a different element.In addition, unless explicitly described to the contrary, the word“comprise” and variations such as “comprises” or “comprising”, will beunderstood to imply the inclusion of stated elements but not theexclusion of any other elements.

In the disclosure, an “image forming job” may denote any one of variousjobs (e.g., printing, copying, scanning, and faxing) related to animage, such as forming an image or generating/storing/transmitting animage file, and a “job” may denote an image forming job, but may alsodenote a series of processes to perform the image forming job.

Also, an “image forming apparatus” refers to an apparatus printing printdata generated in a terminal device such as a computer on a recordingpaper. Examples of the image forming apparatus includes a copier, aprinter, a facsimile, or a multi-function printer (MPF) complexlyrealizing these functions through a single apparatus. The “image formingapparatus may refer to any apparatus capable of performing an imageforming job, such as a printer, a scanner, a fax machine, amulti-function printer (MFP), and a display apparatus.

Also, “hard copy” may refer to an operation of outputting an image to aprinting medium such as paper, and “soft copy” may refer to an operationof outputting an image on a display apparatus such as a TV, a monitor,or the like.

Also, “content” may refer to any type of data that is a target of animage forming job, such as a picture, an image, a document file, and thelike.

Also, “print data” may refer to data converted into a format printableby a printer. Meanwhile, if a printer supports direct printing, a fileitself may be print data.

Also, a “user” may refer to a person who performs an operation relatedto an image forming job using an image forming apparatus or using adevice connected to the image forming apparatus wirelessly or wiredly.Also, “manager” may refer to a person having authority to access everyfunction and system of an “image forming apparatus”. “Manager” and“user” may be the same person.

Unless the types of printing paper are correctly determined or set,original image quality performance may not be ensured, and in theworst-case scenario, the apparatus may be broken down.

Examples of the case that the types of printing paper are incorrectlydetermined may vary, and an example thereof is an influence ofsmoothness, glossiness, a compression degree, etc. In an optical sensormode, a weight or thickness of printing paper in the optical sensorsystem is detected on the basis of strength and weakness of lighttransmitting through the printing paper, i.e., on the basis ofinformation regarding the amount of transmitted light obtained from alight receiving sensor, by irradiating light (generally, infrared light)to the printing paper.

That is, the weight or thickness is detected on the basis of a change inthe amount of the transmitted light depending on whether the printingpaper is heavy/light or thick/thin. However, in case of printing paperhaving high surface smoothness or glossiness and printing paper havinghigh compression, the amount of reflected light increases and the amountof the transmitted light decreases. This may refer to that the amount ofthe transmitted light fluctuates due to factors other than weight, whichdeteriorates detection.

In this connection, FIGS. 9 and 10 illustrate a correlation between theamount of the transmitted light and weight, in which the vertical axisrepresents the amount of the transmitted light as a relative value andthe horizontal axis represents weight (gsm). Here, the amount of thetransmitted light as a relative value indicates a relative amount oftransmitted light of the printing paper with respect to an appropriatelydefined reference value.

As illustrated in FIGS. 9 and 10, a normal smoothness sheet material,which is so-called plain paper, has a certain correlation between theamount of the transmitted light and weight, and therefore, a weight maybe determined on the basis of the correlation. Meanwhile, as shown inFIG. 10, in the case of high smoothness sheet materials (C and D) suchas glossy paper, or the like, the amount of the transmitted lightdecreases, deviating from the correlation between the amount of thetransmitted light and weight as the characteristic of the normalsmoothness sheet material. Therefore, if the weight is determined on thebasis of the above-described correlation, the weight may be erroneouslydetermined.

Referring to the example of FIG. 10, the actual weight of thehigh-smoothness sheet material C is 90 (gsm), but if the weight isdetermined on the basis of the amount of the transmitted light, usingthe characteristic of the normal smoothness sheet material, i.e., thecorrelation between the amount of the transmitted light and weight inthe normal smoothness sheet material, the weight of the high smoothnesssheet material is erroneously determined as 100 (gsm).

Determining smoothness or glossiness of printing paper using an imagepickup device and determining the weight using a correlation between theamount of the transmitted light and weight appropriate for thecorresponding determined glossiness may need a high-priced device suchas a CMOS and may involve complicated processing, resulting in anincrease in cost.

FIG. 1 is a block diagram illustrating a brief configuration of an imageforming apparatus according to an example of the disclosure.

Referring to FIG. 1, an image forming apparatus 100 includes an imageforming part 110, a sensor part 120, and a processor 130.

The image forming part 110 prints print data. As an example, the imageforming part 110 prints print data received through a communicationinterface 140 (to be described later).

Here, the image forming part 110 may perform the printing operation onthe basis of a printing speed, a transfer condition, and a fixingcondition corresponding to a thickness of the recording mediumdetermined by the processor 130 (to be described later). As an example,the recording medium may be printing paper. A configuration of the imageforming part 110 will be described later with reference to FIG. 3.

The sensor part 120 irradiates light to the printing paper and detectsthe amount of transmitted light transmitted through the printing paperand the amount of reflected light reflected from the printing paper ateach of a plurality of positions. As an example, the sensor part 120includes a light emitting part including at least one light emittingelement irradiating light to the printing paper and at least one lightreceiving sensor detecting the amount of the transmitted lighttransmitted through the printing paper among light emitted from thelight emitting element, and the amount of the reflected light reflectedfrom the printing paper. A configuration and operation of the sensorpart 120 will be described later with reference to FIG. 5.

The processor 130 controls each component in the image forming apparatus100. Specifically, the processor 130 may be realized as a centralprocessing unit (CPU), an application specific integrated circuit(ASIC), or the like. As an example, the processor 130 determines whethernew paper is loaded if a loading box is opened or closed. If it isdetermined that new paper is loaded, the processor 130 may performsequential operations to determine a thickness of the input paper.

As an example, the processor 130 may control the sensor part 120 toirradiate light to the printing paper and detect the amount of thetransmitted light and the amount of light reflected from a plurality ofpositions, among the irradiated light.

The processor 130 may determine a thickness of the printing paper on thebasis of the amount of the transmitted light and the amounts of aplurality of reflected lights and control the image forming part 110 toperform a printing operation on the basis of the determined thickness. Aoperation of determining the thickness of the printing paper will bedescribed later in detail with reference to FIG. 4.

When the print data is received, the processor 130 may performprocessing such as parsing on the received print data to generate binarydata and control the image forming part 110 to print the generatedbinary data.

As described above, the image forming apparatus 100 according to theexample determines the thickness of the printing paper in considerationof the amount of calibrated reflected light, as well as the amount ofthe transmitted light, and thus, an influence of a detection inhibitingfactor such as smoothness, glossiness, and the like, of the printingpaper may be suppressed and the thickness may be correctly detected.

In the above description, the printing operation is performed bydetermining the thickness of the paper, but it is also possible toperform the printing operation by determining a weight (gsm) of thepaper in the above-described manner.

Although a simple configuration of the image forming apparatus has beendescribed but various components may be additionally provided when theimage forming apparatus is realized. This will be described below withreference to FIG. 2.

FIG. 2 is a block diagram illustrating a configuration of an imageforming apparatus according to an example of the disclosure.

Referring to FIG. 2, the image forming apparatus 100 according to anexample of the disclosure includes the image forming part 110, thesensor part 120, the processor 130, a communication interface 140, adisplay 150, an operation input part 160, and a storage 170. Here, theimage forming apparatus 100 may be a multi-function peripheral (MPF), orthe like, which complexly realizes a copier, a printer, and a facsimile,or functions thereof through the single apparatus.

The image forming part 110, the sensor part 120, and the processor 130perform the same functions as those of the components of FIG. 1, andthus, a redundant description thereof will be omitted.

The communication interface 140 is connected to a print control terminaldevice (not shown) and receives print data from the print controlterminal device. As an example, the communication interface 140 isformed to connect the image forming apparatus 100 to an external deviceand may also be connected to a terminal device via a local area network(LAN) and the Internet or may be connected thereto via a universalserial bus (USB) port, or a wireless communication (e.g., Wi-Fi802.11a/b/g/n, NFC, Bluetooth) port.

The display 150 displays various types of information provided by theimage forming apparatus 100. As an example, the display 150 may displaya user interface window for selecting various functions provided by theimage forming apparatus 100. The display 150 may be a monitor such as anLCD, a CRT, or an OLED or may be realized as a touch screen capable ofsimultaneously performing a function of the operation input part 160 (tobe described later).

The display 150 may display a control menu for performing a function ofthe image forming apparatus 100.

The display 150 may display a screen for the user to input a distancebetween a light receiving sensor and a light emitting device. A distancebetween at least one of the plurality of light receiving sensors and thelight emitting element may be input through the operation input part160. Meanwhile, such distance information may be input through aseparate distance measurement sensor at the time of implementation ormay be input as a predetermined value by a manufacturer in advance.

The operation input part 160 may receive an input for a functionselected by the user and a control command for the correspondingfunction. Here, the function may include a print function, a copyfunction, a scan function, a fax transmission function, and the like.Such a function control command may be received through a control menudisplayed on the display 150.

The operation input part 160 may be implemented by a plurality ofbuttons, a keyboard, a mouse, and the like, or may be implemented as atouch screen capable of simultaneously performing the function of thedisplay 150 described above.

The storage 170 may store the print data received through thecommunication interface 140. The storage 170 may be realized as astorage medium in the image forming apparatus 100 and an externalstorage medium, i.e., a removable disk including a USB memory, a storagemedium connected to a host, a Web server via a network, or the like.

The storage 170 stores various calibration tables. Here, the calibrationtable may be a calibration table in which initial calibrationcoefficients corresponding to emission characteristics of the lightemitting element are matched in advance or a calibration table in whichconveyance path width calibration coefficients according to distancesbetween a light receiving sensor detecting any one of the amount of thetransmitted light, the amount of regular reflected light, and the amountof diffused reflected light (or diffused reflection) and the lightemitting element.

FIG. 3 is a view illustrating a configuration of an image forming partof FIG. 1 according to an example.

Referring to FIG. 3, the image forming part 110 may include aphotosensitive drum 111, a charger 112, an exposure device 113, adeveloping device 114, a transfer roller 115, a paper transfer part 116,and a fixing device 118.

The image forming part 110 may further include a paper feeding part (notshown) for feeding the recording medium P. An electrostatic latent imageis formed on the photosensitive drum 111. The photosensitive drum 111may be referred to as a photosensitive drum, a photosensitive belt, orthe like, depending on a form thereof.

Hereinafter, for description, a configuration of the image forming part110 corresponding to one color will be described as an example but theimage forming part 110 may include a plurality of photosensitive drums111, a plurality of chargers 112, a plurality of exposure devices 113,and a plurality of developing devices 114 corresponding to a pluralityof colors when realized.

The charger 112 charges a surface of the photosensitive drum 111 to auniform potential. The charger 112 may be realized in the form of acorona charger, a charging roller, a charging brush, or the like.

The exposure device 113 changes a surface potential of thephotosensitive drum 111 according to image information to be printed,thereby forming an electrostatic latent image on the surface of thephotosensitive drum 111. In an example, the exposure device 113 may forman electrostatic latent image by irradiating light modulated accordingto the image information to be printed to the photosensitive drum 111.Such a type of exposure device 113 may be referred to as a scanner, orthe like, and an LED may be used as a light source.

The developing device 114 may accommodate a developer therein andsupplies the developer to the electrostatic latent image to develop theelectrostatic latent image to a visible image. The developing device 114may include a developing roller 117 that supplies the developer to theelectrostatic latent image. For example, the developer may be suppliedfrom the developing roller 117 to the electrostatic latent image formedon the photosensitive drum 111 by a developing electric field formedbetween the developing roller 117 and the photosensitive drum 111.

The visible image formed on the photosensitive drum 111 is transferredto a recording medium P by the transfer roller 115 or an intermediatetransfer belt (not shown). The transfer roller 115 may transfer thevisible image to the recording medium by, for example, an electrostatictransfer method. A visible image is attached to the recording medium Pby electrostatic attraction.

The paper transfer part 116 may pick up the recording medium P from apaper tray and provide the recording medium P to the developing device114. A configuration and operation of the paper transfer part 116 willbe described later with reference to FIG. 4.

The fixing device 118 fixes a visible image on the recording medium P byapplying heat and/or pressure to a visible image on the recording mediumP. The printing operation is completed by the sequential processes.

The above-described developer is used each time the image formingoperation is performed, and runs out when it is used for a predeterminedtime or longer. In this case, a unit for storing the developer (e.g.,the above-described developing device 114 itself may be newly replaced).The parts or components which may be replaced during the use of theimage forming apparatus are called consumable units or replaceableparts, and a memory (or CRUM chip) may be attached to such consumableunits for appropriate management of the corresponding consumable units.

FIG. 4 is a schematic view illustrating a brief configuration forexplaining an arrangement of the sensor part of FIG. 1.

Referring to FIG. 4, the paper transfer part transfers the printingpaper loaded in a paper tray 1 using a plurality of rollers 2, 3 and 9.

The paper tray 1 is a container housing printing paper (a medium forforming a toner image on a surface thereof).

A pickup roller 2 is a roller for picking up the printing paper storedin the paper tray 1.

A feed roller 3 is a roller that moves the printing paper picked up bythe pickup roller 2 to a paper transfer path 4.

The sensor part 120 is provided in the vicinity of the paper transferpath 4 of the printing paper and detects the printing paper beingtransferred. The sensor part 120 may include optical sensors 5 a and 5 bwhich are called a media sensor 5.

A rear conveyance path roller 6 is a roller for conveying the printingpaper on which one side printing has been completed in case of doubleside printing, along a rear conveyance path 7.

The paper transfer path 4 and the rear conveyance path 7 join at ajunction 8 and the printing paper transferred by the feed roller 3 orthe printing paper conveyed by the rear conveyance path roller 6 passesthrough the junction 8.

A register roller 9 is a roller that supplies the printing paper, whichhas passed through the junction 8, to the transfer roller 115.

The transfer roller 115 is provided at a position opposing thephotosensitive drum 111. When the printing paper is supplied between thetransfer roller 115 and the photosensitive drum 111 by the registerroller 9, the transfer roller 115 rotates to allow the printing paper tocome into close contact with the photosensitive drum 111 and allow atoner to be transferred to the printing paper as a bias having apolarity opposite to that of the photosensitive drum 111 is applied.

An image formation and conveyance part 12 discharges the printing paperto which the toner has been transferred by the transfer roller 10 to theoutside, or, in case of double-sided printing, the image formation andconveyance part 12 provides the printing paper which has been one-sideprinted to the rear conveyance path 7.

The processor 130, which is a semiconductor device equipped with a CPU,performs various control processing, arithmetic processing, and thelike, of the image forming apparatus.

The processor 130 acquires a voltage value output from each lightreceiving sensor configuring the sensor part 120 by executing variousprograms and serves to determine a type of the printing paper beingconveyed on the basis of the acquired voltage value. Also, the processor130 has a function of executing printing by selecting appropriateprinting conditions such as a conveyance speed, a transfer condition, afixing condition, and the like, of the printing paper according to thedetermined type of the paper.

One of items of the types of printing paper to be determined is a weightor thickness of the printing paper and the processor 130 determines thison the basis of an output value from each light receiving sensorconfiguring the sensor part 120. Therefore, the processor 130 may have afunction as a thickness determining part.

Also, the voltage value of each sensor, which indicates the amount ofreceived light detected by each light receiving sensor provided in thesensor part 120, is converted from an analog signal to a digital signalby an A/D converter (not shown) and provided as the digital signal tothe processor 130.

FIG. 5 is a conceptual view illustrating an operation of the sensor part120 of the image forming apparatus of the example.

The sensor part 120 includes a light emitting part 21 and a plurality oflight receiving parts 22, 23, and 24.

The light emitting part 21 is an optical component such as a lightemitting element that emits light. The light emitting part 21 may beconfigured as a light emitting element itself or may be configured as amember including at least one light emitting element. As a highperformance and low-priced light emitting element, for example, a lightemitting diode (LED) may be used.

A transmitted light receiving part 22 is provided and substantiallyaligned with an optical path of light emitted from the light emittingpart 21 and detects the amount of the transmitted light which is theamount of light transmitted through the printing paper being transferredalong the paper transfer path 4, among light emitted from the lightemitting part 21.

A regular reflected light receiving part 23 is installed at a positionat which the amount of the regular reflected light, which is the amountof light regularly reflected by the printing paper being transferredalong the paper transfer path 4, among the light emitted from the lightemitting part 21, is detected.

A diffused reflected light receiving part 24 is provided at a positionat which the amount of the diffused reflected light, which is the amountof light diffused and reflected by the printing paper, among the lightemitted from the light emitting part 21, is detected.

For example, a photodiode (PD) or a phototransistor (PTr) may be used asa light receiving element configuring the transmitted light receivingpart 22, the regular reflected light receiving part 23, and the diffusedreflected light receiving part 24. Further, in the image formingapparatus of the example, as described above, each of the amount of thetransmitted light, the amount of the regular reflected light, and theamount of the diffused reflected light are handled as a voltage valueoutput by each light receiving sensor.

FIGS. 6 and 7 are views illustrating examples of calibration tablesstored in the storage of FIG. 2. As an example, FIG. 6 is a viewillustrating an example of a table relating to a conveyance path widthcalibration coefficient Km and FIG. 7 is a view illustrating an exampleof a table relating to an initial calibration coefficient Ka.

These calibration tables A and B are stored in a memory of the processor130 or in a memory outside the processor 130. The calibration table A isa table in which the conveyance path width calibration coefficients Kmcorresponding to distances between the light emitting part 21 and anyone of the light receiving parts (the transmitted light receiving part22 in this example) are matched in advance, and the calibration table Bis a calibration table in which the initial calibration coefficients Kacorresponding to emission characteristics of the light emitting part 21are matched in advance.

The conveyance path width calibration coefficient Km is a calibrationcoefficient for calibrating a difference in configuration based onmodels of the image forming apparatus and is a calibration coefficientdefined according to distances between the light emitting element andthe light receiving sensor. As illustrated in FIG. 6, in the example, anintegers of 1 to 3 are assigned according to distances between the twosensors 5 a and 5 b configuring the media sensor 5.

The calibration table (A) allows the functions related to the disclosureto be used universally in a plurality of models. When mounted on amodel, the transport path width calibration coefficient Km is determinedfrom the calibration table A on the basis of a distance between thesensors 5 a and 5 b of the corresponding model. The processing isexecuted at the time of manufacturing the apparatus, or the like, andthus, the value of the conveyance path width calibration coefficient Kmis stored in the memory of the processor 130 or an external memory ofthe processor 130.

The initial calibration coefficient Ka is a calibration coefficient forcalibrating a difference or variation of the emission characteristics ofthe light emitting part 21. As illustrated in FIG. 7, in this example,integers of 1 to 6 are assigned according to the amount of calibratedlight. In this example, 1 and 2 are reserved and are not used here.

The amount of calibrated emitted light is a numerical value indicating acalibration percentage of the amount of light in calibration processingof increasing the amount of light performed to supplement the amount oflight when the amount of emitted light from the light emitting part 21is lowered due to deterioration with time or a temperature change, forexample. For example, when the amount of light from the light emittingpart 21 is lower than a predetermined value, calibration is performed toincrease the amount of emitted light from the light emitting part 21 by10%, and here, 10% is the amount of calibrated emitted light. The amountof emitted light is performed by increasing a pulse width modulation(PWM) value for driving an LED which emits light. The amount of emittedlight is calibrated, for example, when the apparatus is turned on,immediately before printing is performed, or at every predeterminedinterval, and the like, and a resultant amount of calibrated emittedlight is logged.

In the image forming apparatus of the example, as described below,robustness against variations in the amount of emitted light from thelight emitting part 21 is high. Therefore, although the amount of lightemitted from the light emitting part 21 is changed, the processing maybe continued without calibrating the amount of emitted light itself in aconsiderable portion. However, if the amount of emitted light issignificantly reduced to exceed a predetermined value, the amount ofemitted light is calibrated.

The table of FIG. 7 is information set for changing the initialcalibration coefficient Ka in accordance with the amount of calibratedemitted light when the amount of emitted light is significantly changedso it is calibrated. Also, in the example, 3 is set as an initial valueof the initial calibration coefficient Ka.

Hereinafter, the outline of a process of determining a weight ofprinting paper according to the disclosure in the image formingapparatus of the example having the above configuration will bedescribed with reference to FIG. 8. In the following description, aprocessing subject of each processing is omitted, but the followingprocessing is executed by the processor 130.

FIG. 8 is a schematic view of a process of determining a weight ofprinting paper. This process is executed in a state in which printingpaper is transferred along the paper transfer path 4 and the printingpaper is caught in the sensor part 120, i.e., in a state in which lightfrom the light emitting part 21 of the sensor part 120 is irradiated tothe printing paper and reflected light or transmitted light from theprinting paper is obtained.

First, in operation S801, light is irradiated from the light emittingpart 21 to the printing paper, and the amount of light transmittedthrough the printing paper, the amount of regularly reflected light, andthe amount of the diffused reflected light are obtained from thetransmitted light receiving part 22, the regular reflected lightreceiving part 23, and the diffused reflected light receiving part 24,respectively. As described above, outputs from the respective lightreceiving parts are voltages and voltage values A/D-converted from thecorresponding voltages are input to the processor 130.

In operation S802, it is determined whether an increase calibrationvalue is 0 (i.e., the amount of emitted light is not increased) orwhether the increase calibration value exceeds 20%.

As described above, the increase calibration value is logged (stored inthe memory) in accordance with results of the calibration process of theamount of emitted light which is executed separately, and thedetermination in operation S802 is performed on the basis of thecorresponding log (later operation S803 is the same).

If the increase calibration value is 0, the process proceeds tooperation S807 (to be described later).

Meanwhile, if the increase calibration value exceeds 20%, errorprocessing is performed in operation S809 and the process is terminated.As described hereinafter, in the image forming apparatus according tothe example, robustness against a change in the amount of emitted lightfrom the light emitting part 21 is high, and unless the amount ofemitted light from the light emitting part 21 is changed by 60% orgreater (a predetermined change proportion) with respect to an initialvalue, the amount of emitted light is not calibrated. When the amount ofemitted light is changed by 60% or greater with respect to the initialvalue, that is, when the amount of emitted light is reduced to 40 orless with respect to the initial value as 100, the amount of emittedlight is first increased. In an example of this example, on the basis ofthe initial value as 100, the increase calibration value is set to 5 to0% when the amount of emitted light is 35 to 40, set to 10 to 5% whenthe amount of emitted light is 30 to 35, and set to 20 to 10% when theamount of emitted light is 20 to 30.

That is, the increase calibration value exceeding 20% indicates that theamount of emitted light from the light emitting part 21 is changed by80% (predetermined upper limit value) or greater with respect to theinitial value, and in this case, It is determined that the life thelight emitting element of the light emitting part 21 has ended or thelight emitting element has a fault, and error processing (operationS809) is performed. The error processing is processing such as stoppingthe print processing, displaying a warning, log of error contents, andthe like.

If the increase calibration value is not 0 and does not exceed 20%,operation S803 is performed (operation S802: NO→operation S803). Theprocessing of operations S803 to S806 is processing for changing theinitial calibration coefficient Ka on the basis of the setting of thecalibration table B (FIG. 7) according to the increase calibrationvalue.

If the increase calibration value is greater than 0 and equal to orsmaller than 5%, the initial calibration coefficient Ka is set to 4(operation S803→operation S804).

If the increase calibration value is greater than 5% and equal to orsmaller than 10%, the initial calibration coefficient Ka is set to 5(operation S803→operation S805).

If the increase calibration value is greater than 10% and equal to orsmaller than 20%, the initial calibration coefficient Ka is set to 6(operation S803→operation S806).

When the increase calibration value is 0, the processing of changing theinitial calibration coefficient Ka in operations S803 to S806 is skipped(operation S802→operation S807), and thus, the value of the initialcalibration coefficient Ka is 3 (initial value). Here, operations S801to S809 are performed once, but in case of considering repetitionprocessing after the processing is first performed, it is necessary toperform processing of returning the initial calibration coefficient Kato 3 after operation S807 or S808.

After the initial calibration coefficient Ka is determined in operationsS802 to S806, a thickness coefficient K_(thickness) is calculated on thebasis of the following equation in operation S807.

In following Equation 1, V_(trans) denotes the amount of the transmittedlight, V_(ref) denotes the amount of the regular reflected light,V_(diff) denotes the amount of the diffused reflected light, km denotesa conveyance path width calibration coefficient, and Ka denotes aninitial calibration coefficient. In the example, each amount of light isa value obtained by A/D-converting a voltage output from each lightreceiving part, as described above.

$\begin{matrix}{K_{thickness} = {\frac{V_{trans}}{V_{diff}^{k\; m}} + {{ka}*\left( {\frac{V_{ref}}{V_{diff}} - 1} \right)}}} & {\langle{{Equation}\mspace{14mu} 1}\rangle}\end{matrix}$

The image forming apparatus of the example is capable of restraining theinfluence of detection inhibiting factors such as smoothness,glossiness, and the like, of printing paper and detecting a correctweight and has a basic concept of ‘calibrating a change in the amount ofthe transmitted light, which is caused due to smoothness of paper, by areflected light component’.

Detecting a weight of printing paper using the optical sensor isperformed using the fact that there is a certain correlation between theamount of the transmitted light and the weight. That is, as illustratedin FIGS. 9 and 7, the weight is determined on the basis of the detectedamount of transmitted light, on the basis of the correlation between theamount of the transmitted light and the weight.

However, compared with a normal smoothness sheet material, which isso-called plain paper, in high smoothness sheet material having highsurface smoothness and glossiness, the amount of the regular reflectedlight and the amount of the diffused reflected light tend to increaseand the amount of the transmitted light tends to decrease. As a result,the correlation between the amount of the transmitted light and theweight is different from that of the normal smoothness sheet material,and thus, determining the weight of the high smoothness sheet materialon the basis of the correlation between the amount of the transmittedlight and the weight in the normal smoothness sheet material may end upwith erroneous determining. Therefore, weight detection may not beperformed on the basis of the correlation between the amount of thetransmitted light and the weight in the normal smoothness sheetmaterial, that is, a single evaluation reference. As a solution, aplurality of evaluation references may be provided and a separateprocessing may be provided to determine smoothness or glossiness ofprinting paper, which, however, incurs cost.

In contrast, the image forming apparatus of the example calibrates thereduced amount of transmitted light using the amount of the reflectedlight and using the phenomenon that the amount of regular reflected andthe amount of diffused reflected light increase while the amount of thetransmitted light decreases in a high smoothness sheet material, wherebya weight of printing paper in which smoothness or glossiness of asurface thereof is different may be determined using a single evaluationreference (correlation). That is, it is possible to detect the weight ofthe printing paper with high robustness against detection inhibitingfactors such as smoothness, glossiness, or the like, of the printingpaper.

In addition, the image forming apparatus of the example has highrobustness against a change (deterioration with time or temperature) inthe amount of light itself from a light source (light emitting part 21).

FIG. 13 is a graph showing comparison of correlation between a weight ofprinting paper and the amount of the transmitted light when the amountof emitted light from a light source itself is changed. In this graph,transmission 1 marked by the rhomboid plots represents the amount of thetransmitted light when the light source is in an initial state (theamount of emitted light of 100%) and transmission 2 marked by the squareplots represents the amount of the transmitted light when the amount ofemitted light from the light source was reduced by 60%. The verticalaxis indicates the amount of the transmitted light as a relative value.Here, the “amount of transmitted light as a relatively value”comparatively indicates a relative amount of the amount of thetransmitted light of the printing paper with respect to an appropriatelydefined reference value. As illustrated FIG. 13, if the amount ofemitted light from the light source itself is reduced, the amount of thetransmitted light also naturally decreases, and thus, a correlationbetween the amount of the transmitted light and the weight is alsochanged.

In contrast, when the amount of light itself from the light source(light emitting part 21) is changed, the image forming apparatus of theexample calibrates (normalize) the amount of the transmitted light usingthe amount of the reflected light by considering the fact that theamount of the regular reflected light and the amount of the diffusedreflected light, as well as the amount of the transmitted light, arealso equally changed. Therefore, although the amount of emitted lightitself from the light source is changed, the weight of the printingpaper may be determined using the single evaluation reference.

FIG. 14 is a graph illustrating a change in the amount of thetransmitted light when the amount of emitted light from a light sourceis changed and stability of a value obtained by normalizing the amountof the transmitted light with the amount of the diffused reflectedlight. In this graph, the horizontal axis represents an output value(voltage value) of a light receiving sensor. As illustrated FIG. 14, ifthe amount of emitted light from the light source itself decreases, theamount of the transmitted light also naturally also decreases, which is,thus, not appropriate for correlation between the amount of thetransmitted light and the weight described above.

In contrast, when the amount of light itself from the light source(light emitting part 21) is changed, the image forming apparatus of theexample calibrates (normalize) the amount of the transmitted light usingthe amount of the reflected light by considering the fact that theamount of the regular reflected light and the amount of the diffusedreflected light, as well as the amount of the transmitted light, arealso equally changed. Therefore, although the amount of emitted lightitself from the light source is changed, the weight of the printingpaper may be determined using the single evaluation reference. Asillustrated in FIG. 14, the amount of the transmitted light and theamount of the diffused reflected light are changed according to a changein the amount of emitted light itself from the light source, while theamount of the transmitted light (normalized voltage (V): triangularplots) normalized using the amount of the diffused reflected light is astabilized value. That is, it is possible to detect the weight with highrobustness against the detection inhibiting factor of the change in theamount of light itself from the light source (light emitting part 21).

To realize robustness against the detection inhibiting factors such assmoothness and glossiness of the printing paper, Equation 1 has a formthat the value (the amount of calibrated transmitted light) equivalentto the transmitted light is calibrated (added) using the value (theamount of the calibrated reflected light) equivalent to the reflectedlight.

In addition, to realize robustness against the detection inhibitingfactor of the change in the amount of light itself from the lightsource, the amount of the transmitted light is normalized on the basisof the amount of the diffused reflected light and the conveyance pathwidth calibration coefficient Km.

That is, “V_(trans)/(V_(diff) ^(km))” represents the pure amount oftransmitted light through the printing paper and the amount of detectedlight diffused and reflected from the surface, respectively, and aims atbeing normalized to different absolute amounts. A more stable physicalproperty value is obtained by converting the transient irregularity atthe time of each detection into a normalized amount as a relativerelation.

Further, ka*(V_(ref)/V_(diff))−1 represents surface smoothness of theprinting paper, and as the relation of V_(ref)>V_(diff) is stronger, thesurface smoothness is higher. In terms of a configuration of the mediasensor 5 of the example, it is easier to detect the amount of theregular reflected light than the amount of the diffused reflected light,and in case that the regular reflection component increases according tohigh smoothness, it may be sensitively reacted by the regular reflectedcomponent.

In this manner, as for the amount of the transmitted light whichdecreases as smoothness of the printing paper increases, the reducedamount of the transmitted light is calibrated to be preserved using thecomponent increased as smoothness of the printing paper increases, thusrealizing robustness against the detection inhibiting factors such assmoothness, glossiness, and the like, of the printing paper.

Also, because the regular reflected light receiving part 23 receivesboth the regular reflected light and the diffused reflected light, anoutput value from the regular reflected light receiving part 23 is avalue representing the sum of the amount of the diffused reflected lightand the amount of the regular reflected light. That is,

The output value of regular reflected light receiving part 23 the amountof the diffused reflected light+the amount of the regular reflectedlight, and

Therefore, the amount of regular reflected light the output value of theregular reflection light receiving part 23−the amount of the diffusedreflected light

Therefore, the amount of regular reflected light/the amount of diffusedreflected light (the output value of regular reflected light receivingpart 23−the amount of diffused reflected light)/the amount of diffusedreflected light, and

The right side may be modified to

(The output value of the regular reflected light receiving part 23/theamount of diffused reflected light)−1

That is, “(the amount of regular reflected light/the amount of diffusedreflected light)−1” or “(V_(ref)/V_(diff))−1” ink {(the amount ofregular reflected light/the amount of diffuse reflected light)−1} inEquation 2 or ka {(V_(ref)/V_(diff))−1} in Equation 1 normalizes theamount of regular reflected light on the basis of the amount of diffusedreflected light.

Returning to FIG. 8, description is continued.

In operation S807, after the thickness coefficient K_(thickness) iscalculated on the basis of Equation 1 described above, the weight of theprinting paper is determined on the basis of the thickness coefficientK_(thickness) in operation S808 and the weight determination processingis terminated.

The “determining the weight of the printing paper on the basis of thethickness coefficient K_(thickness)” is determining the weightcorresponding to the thickness coefficient K_(thickness) calculated byperforming operations S801 to S807 on the basis of the correlationbetween the thickness coefficient K_(thickness) and the weight of theprinting paper as illustrated in FIG. 12.

In the description of Equation 1 above, the thickness coefficientK_(thickness) is a coefficient representing the weight of the printingpaper having robustness for both the detection inhibiting factor such assmoothness, glossiness, and the like, of the printing paper and thedetection inhibiting factor such as a change in the amount of lightitself from the light source. Therefore, it is possible to allow thethickness coefficient K_(thickness) and the weight to have a correlationof the robustness against the two inhibiting factors. That is, asillustrated in FIG. 12, the same correlation may be provided for any oneof the normal smoothness sheet material (K_(thickness)_normal) and thehigh smoothness sheet material (K_(thickness)_low), and the weight maybe determined on the basis of the single indicator (correlation).

In addition, the correlation between the thickness coefficientK_(thickness) and the weight is set in advance in the apparatus, and maybe set as a table or set by an equation, or the like.

Regarding the above-described weight determination, evaluations based onthe results of detecting the amount of the transmitted light, the amountof the regular reflected light, and the amount of the diffused reflectedlight of printing paper are shown below.

Four types of printing paper A to D were prepared.

A: Normal smoothness sheet material, weight ⋅ ⋅ ⋅ 90 (gsm)

B: Normal smoothness sheet material, weight ⋅ ⋅ ⋅ 100 (gsm)

C: High smoothness sheet material, weight ⋅ ⋅ ⋅ 90 (gsm)

D: High smoothness sheet material, weight ⋅ ⋅ ⋅ 100 (gsm)

FIG. 11 is a table illustrating voltage values as detection results ofthe amount of the transmitted light, the amount of the regular reflectedlight, and the amount of the diffused reflected light for each of thenormal smoothness sheet materials A and B and the high smoothness sheetmaterials C and D. It is also a table illustrating coefficients(thickness coefficient K_(thickness), conveyance path width calibrationcoefficient Km, initial calibration coefficient Ka) regarding theabove-described weight determination. Here, the case that the conveyancepath width calibration coefficient Km defined according to models of theapparatus is 1 and the initial calibration coefficient Ka is 3 (theinitial value as is) is taken as an example.

The graphs of FIGS. 9 and 10 are plotting the results of the abovedetection. In particular, FIG. 10 is a graph in which a portion of theplots A to D is enlarged.

Referring to FIGS. 9 and 10, the normal smoothness sheet materials A andB, which are both plain paper, are included in the correlation (normalsmoothness sheet material characteristics) illustrated in the figures.In contrast, the high smoothness sheet materials C and D such as glossypaper are not included in the correlation because the amount of thetransmitted light decreases. Therefore, determining a weight on thebasis of the above-described correlation may end up with erroneousdetermination. As to the example of FIG. 10, the actual weight of thehigh smoothness sheet material C is 90 (gsm) but it is erroneouslydetermined as 100 (gsm).

Meanwhile, FIG. 12 plots a relationship between the thicknesscoefficient K_(thickness) and the weight on the basis of the thicknesscoefficient K_(thickness) calculated by the above-described processingbased on each detection value.

As illustrated in the figure, all the normal smoothness sheet materialsA and B and the high smoothness sheet materials C and D have the samecorrelation between the thickness coefficient K_(thickness) and theweight, and thus, it is possible to detect a weight with high robustnessagainst detection inhibiting factors such as smoothness and glossinessof printing paper.

As described above, the image forming apparatus of the example iscapable of detecting a weight with high robustness against the detectioninhibiting factors such as smoothness and glossiness of printing paperby calibrating (preserving a reduction in the amount of the transmittedlight) the amount of the transmitted light, which decreases assmoothness of the printing paper is high, using the component whichincreases as smoothness of the printing paper is high, on the basis ofEquation 1 (or Equation 2). As a result, high robustness against thedetection inhibiting factors such as smoothness and glossiness of theprinting paper may be obtained by the optical sensor, without a membersuch as a separate image pickup device, or the like, and is very useful.

Further, because the amount of the transmitted light is normalized usingthe amount of the diffused reflected light, it is possible to detect theweight with high robustness against the detection inhibiting factor of achange in the amount of light itself from the light source (a lightemitting part 21). Accordingly, even when the amount of light from thelight source is changed (basically, the amount of light is reduced) dueto a change in an environment such as aged deterioration, a hightemperature and humidity, and the like, it is possible to detect theweight, in particular, without having to perform calibration, or thelike. The image forming apparatus of the example may be able to detectthe weight, even without calibrating the amount of emitted light, unlessthe amount of light from the light source is changed by 60% or greaterwith respect to the initial value.

In case that the amount of emitted light from the light source ischanged due to aged deterioration, or the like, and an output value fromany one of the light receiving parts is accordingly changed, if aproportion of the corresponding change to a predetermined referencelight emission amount exceeds a predetermined change proportion (60%),processing of adjusting the amount of emitted light from the lightemitting part 21 is executed and processing of changing the initialcalibration coefficient Ka is performed accordingly. Thus, even afterthe amount of emitted light from the light emitting part 21 is adjusted,the weight determination may be correctly performed. Also, when theproportion of the corresponding change exceeds the predetermined upperlimit value (80%), error processing is performed to inform a user aboutan error of the apparatus.

In the example, for example, the thickness coefficient K_(thickness) iscalculated based on Equation 1 using the voltage values which are outputvalues from the light receiving parts as values indicating the amount ofthe transmitted light, the amount of the diffused reflected light, andthe amount of the regular reflected light, respectively.

That is, the case of using the output values (voltage values) from therespective light receiving parts as the values of the amount of thetransmitted light, the amount of the diffused reflected light, and theamount of the regular reflected light in Equation 2 is used as anexample, but the disclosure is not limited thereto. For example, valuesobtained by normalizing the output values from the respective lightreceiving parts may be used as values representing the respectiveamounts of light in Equation 2 below, or the amount of the transmittedlight as a relative value may also be used.

$\begin{matrix}{K_{thickness} = {\frac{{amount}\mspace{14mu} {of}\mspace{14mu} {transmitted}\mspace{14mu} {light}}{{{amount}\mspace{14mu} {of}\mspace{14mu} {diffuse}} - {{reflected}\mspace{14mu} {light}^{k\; m}}} + {{Ka}^{*}\left( {\frac{{{amount}\mspace{14mu} {of}\mspace{14mu} {regular}} - {{reflected}\mspace{14mu} {light}}}{{{amount}\mspace{14mu} {of}\mspace{14mu} {diffuse}} - {{reflected}\mspace{14mu} {light}}} - 1} \right)}}} & {\langle{{Equation}\mspace{14mu} 2}\rangle}\end{matrix}$

Here, the coefficient K_(thickness) denotes the thickness coefficient,km denotes a conveyance path width calibration coefficient determinedaccording to a distance between any one of light receiving sensorsdetecting the amount of the regular reflected light, the amount of thediffused reflected light, and the amount of the transmitted light andthe light emitting element, and ka denotes the initial calibrationcoefficient determined according to emission characteristics of thelight emitting element.

The “values obtained by normalizing the output values from therespective light receiving part” are the ratio of output values of thelight receiving part when printing paper as a measurement target isinterposed to an output value of the light receiving part when light isreceived without interposing the paper or an output value of the lightreceiving part when a reference sheet is interposed. Also, the “amountof transmitted light as a relative value” comparatively indicates arelative amount of the amount of the transmitted light (output value ofthe light receiving part) of the printing paper with respect to anappropriately defined reference value.

The concept of the disclosure is to calibrate a change in the amount ofthe transmitted light by the reflective light component using a valuewhich may represent each of the amount of the transmitted light, theamount of the diffused reflected light, and the amount of the regularreflected light. Therefore, for example, the amount of the transmittedlight, the amount of the diffused reflected light, and the amount of theregular reflected light in Equation 2 are not limited to the values thatdirectly represent the amount of light itself (e.g., lumen, etc.) andmay be values which may correspond to the respective amounts of lightsuch as the voltage values as output values from the respective lightreceiving parts described in the example or the normalized valuesdescribed above.

In this example, the case that the conveyance path width calibrationcoefficient Km is set in advance in the apparatus by calibration, or thelike, in the manufacturing process is taken as an example but thedisclosure is not limited thereto. For example, a sensor for measuring adistance between the light emitting element and any one of the lightreceiving sensors or an input part for receiving an input of informationcorresponding to the distance between the light emitting element and anyone of the light receiving sensors may be provided and the conveyancepath width calibration coefficient Km may be set with reference to acalibration table A (FIG. 6) on the basis of an obtained distancebetween the sensors. Here, as for the input “information correspondingto the distance between the light emitting element and any one of thelight receiving sensors”, for example, a table in which product names ormodel names are matched to the distances between sensors is provided anda distance between the sensors may be determined on the basis of aninput of a product name or a model name. In this case, the product name,the model name, and the like, is “information corresponding to thedistance between the light emitting element and any one of the lightreceiving sensors”. Also, the input part may be a user interfacereceiving an input from a person (service man, user, etc.) or may be aninterface (regardless of whether it is wired or wireless interface)receiving an input from an external device.

The conveyance path width calibration coefficient Km and the initialcalibration coefficient Ka may be appropriately determined inconsideration of the characteristics of each apparatus. A calculationmethod in Equation 2 may be changed according to determination of anumerical value thereof. That is, in the disclosure, the amount of thediffused reflected light is exponentiated from the conveyance path widthcalibration coefficient Km, for example, but the calculation method maybe changed according to methods for defining the conveyance path widthcalibration coefficient Km or characteristics of the apparatus. Forexample, the conveyance path width calibration coefficient Km may bemultiplied to the amount of diffuse reflected amount so as to becalibrated. This is the same with the initial calibration coefficientKa. Calibration using the conveyance path width calibration coefficientKm or the initial calibration coefficient Ka is calibration forprecisely or efficiently executing the processing of determining aweight based on the concept described above in an apparatus and may beappropriately optimized for an individual apparatus.

In the example, determining a weight is described but a thickness mayalso be determined. The correlation between the thickness coefficientK_(thickness) and a thickness of printing paper may be provided, insteadof the correlation between the thickness coefficient K_(thickness) andthe weight of printing paper illustrated in FIG. 12.

In this example, the case that the media sensor (optical sensor)includes the transmitted light receiving part (transmitted lightreceiving sensor), the regular reflected light receiving part (regularreflected light receiving sensor), and the diffused reflected lightreceiving part (diffused reflected light receiving sensor) and eachsensor detects the amount of the transmitted light, the amount of theregular reflected light, and the amount of the diffused reflected lightis taken as an example, but one or two sensors may be used for detectingthe amount of the transmitted light, the amount of regular reflectedlight, and the amount of the diffused reflected light.

FIG. 15 is a view illustrating a media sensor (optical sensor) includingtwo light receiving sensors. In this example, a transmitted lightreceiving part 22′ (first light receiving sensor) and a reflected lightreceiving part 23′ (second light receiving sensor) are provided.

The transmitted light receiving part 22′ and the reflected lightreceiving part 23′ are configured to rotate in a measurement plane whichis a plane including an optical axis perpendicular to printing paperbased on a measurement point as an intersection point of an optical axisof the light emitting part 21 and the printing paper. As illustrated inFIG. 15, the transmitted light receiving part 22′ is configured torotate in a range opposite to the light emitting part 21 with respect tothe printing paper, and the reflected light receiving part 23′ may beconfigured to rotate in a range which is the side where the lightemitting part 21 is present with respect to the printing paper.

In the media sensor having such a configuration, the amount of receivedlight is measured by rotating the transmitted light receiving part 22′in a predetermined range (e.g., in the range of 20 to 70° as illustratedin FIG. 15) and a peak value thereof is obtained as the amount of thetransmitted light. Similarly, the amount of received light is measuredby rotating the reflected light receiving part 23′ in a predeterminedrange (e.g., in the range of 20 to 70° as illustrated in FIG. 15), apeak value thereof is obtained as the amount of the regular reflectedlight, and an appropriately selected value is used as the amount of thediffused reflected light (e.g., a measurement value at a predeterminedangle is used, etc.).

In the processing of measuring the amount of received light, whilerotating the transmitted light receiving part 22′ or the reflected lightreceiving part 23′, the amount of received light may be measured, whileconveying the printing paper, and if this is difficult due to arelationship of a conveyance speed of the printing paper with respect toa rotation speed of the light receiving part, the measurement may beperformed by stopping conveying (or by lowering the speed).

The processing after obtaining the respective amounts of received lightis the same as that of the above example.

As illustrated in FIG. 15, by using the single sensor to detect theamount of the regular reflected light and the amount of the diffusedreflected light, the number of the light receiving sensors may bereduced and a proportion of the amount of the regular reflected lightand the amount of the diffused reflected light may not need to becalibrated. Also, by detecting the amount of received light in apredetermined range (e.g., the range of 20 to 70° as illustrated in FIG.15), a peak value thereof may be accurately obtained, and because aprofile of the amount of light is obtained in the predetermined range,it is possible to use the corresponding information to determine a typeof paper.

Also, in FIG. 15, the case that two light receiving sensors includingthe transmitted light receiving part 22′ (first light receiving sensor)and the reflected light receiving part 23′ (second light receivingsensor) are provided is described as an example, but a single lightreceiving sensor configured to rotate from one side of the lightemitting part 21 to the opposite side thereof with respect to theprinting paper may also be provided. In this case, if it is difficult torotate with the printing paper, the corresponding printing paper may beconveyed, and thereafter, the amount of received light on the oppositeside in next printing paper may be detected. In this case, however, thecorresponding subsequent printing paper is to be the same type of paper.

FIG. 16 is a flowchart illustrating a thickness determining methodaccording to an example of the disclosure.

Referring to FIG. 16, light is irradiated to printing paper in operationS1610. As an example, light may be irradiated to the printing paperusing a light emitting element that emits light.

The amount of the transmitted light transmitted through the printingpaper and the amount of the reflected light reflected from the printingpaper are detected from each of a plurality of positions in operationS1620. As an example, the amount of the transmitted light and theamounts of a plurality of reflected lights may be detected using aplurality of light receiving elements. Meanwhile, when realized, a lightreceiving sensor may be configured to be rotatable and the single lightreceiving sensor may be used as illustrated in FIG. 15.

Thereafter, a thickness of the printing paper is determined on the basisof the amount of the transmitted light and the amounts of the pluralityof reflected lights in operation S1620. As an example, the amount of thecalibrated transmitted light may be calculated by normalizing the amountof the transmitted light on the basis of the amount of first reflectedlight among the amounts of the plurality of reflected lights, the amountof the calibrated reflected light may be calculated by normalizing theamount of second reflected light different from the amount of the firstreflected light on the basis of the amount of the first reflected light,a thickness coefficient may be calculated by adding the amount of thecalibrated transmitted light and the amount of the calibrated reflectedlight, and a thickness of the printing paper may be determined on thebasis of the calculated thickness coefficient.

Thereafter, an image is formed on the printing paper on the basis of thedetermined thickness in operation S1640. As an example, a printingoperation may be performed by adjusting a printing speed, a fixingstate, and a developing state on the basis of the determined thicknessof the printing paper.

Therefore, in the image forming method according to the example, thethickness of the printing paper is determined in consideration of theamount of the calibrated reflected light, as well as the amount of thetransmitted light, an influence of the detection inhibiting factors suchas smoothness and glossiness of the printing paper may be suppressed andthe correct thickness may be detected. The image forming method asillustrated in FIG. 16 may be executed on an image forming apparatushaving the configuration of FIG. 1 or FIG. 2 and may also be executed onan image forming apparatus having other configurations.

In addition, the image forming method as described above may beimplemented as at least one executable program for executing the imageforming method as described above, and the executable program may bestored in a computer-readable recording medium.

While the disclosure has been described with reference to theaccompanying drawings, it is to be understood that the scope of thedisclosure is defined by the claims described hereinafter and should notbe construed as being limited to the above-described examples and/ordrawings. It is to be clearly understood that improvements, changes, andmodifications that are obvious to those skilled in the art are alsowithin the scope of the disclosure as defined in the claims.

What is claimed is:
 1. An image forming apparatus comprising: an imageforming device to form an image on a printing medium; a sensor toirradiate light to the printing medium, detect an amount of lighttransmitted through the printing medium, and detect an amount of lightreflected from the printing medium to each of a plurality of positions;and a processor to determine a thickness of the printing medium based onthe amount of light transmitted through the printing medium and theamount of light reflected from the printing medium to each of theplurality of positions, and control the image forming device based onthe determined thickness.
 2. The image forming apparatus as claimed inclaim 1, wherein the processor is to calculate an amount of calibratedtransmitted light by normalizing the amount of the transmitted lightthrough the printing medium based on an amount of a first reflectedlight among the light reflected from the plurality of positions,calculate an amount of calibrated reflected light by normalizing anamount of a second reflected light different from the amount of thefirst reflected light based on the amount of the first reflected light,and calculate a thickness coefficient by adding the amount of thecalibrated transmitted light and the amount of the calibrated reflectedlight, and determine the thickness of the printing medium based on thecalculated thickness coefficient.
 3. The image forming apparatus asclaimed in claim 2, wherein the amount of the first reflected light isan amount of diffused reflected light and the amount of the secondreflected light is an amount of the regular reflected light.
 4. Theimage forming apparatus as claimed in claim 2, further comprising: astorage to store a calibration table in which initial calibrationcoefficients according to emission characteristics of a light emittingelement irradiating light to the printing medium are matched in advance,wherein the processor is to calculate the amount of the calibratedreflected light based on a value obtained by normalizing the amount ofthe second reflected light based on the amount of the first reflectedlight and the initial calibration coefficient.
 5. The image formingapparatus as claimed in claim 4, wherein the initial calibrationcoefficient is updated when an output value of any one of lightreceiving sensors detecting the amount of the first reflected light, theamount of the second reflected light, and the amount of the transmittedlight is changed based on a change in the amount of emitted light fromthe light emitting element and a proportion of the change in outputvalue to a predetermined reference light emission amount exceeds apredetermined proportion.
 6. The image forming apparatus as claimed inclaim 2, further comprising: a storage to store a calibration table inwhich conveyance path width calibration coefficients according todistances between a light receiving sensor detecting any one of theamount of the transmitted light, an amount of regular reflected light,and an amount of the diffused reflected light and the light emittingelement are matched in advance, wherein the processor is to determine aconveyance path width calibration coefficient based on the distancebetween the light receiving sensor and the light emitting element, andis to calculate the amount of the calibrated transmitted light bynormalizing the amount of the transmitted light based on the conveyancepath width calibration coefficient and the amount of the first reflectedlight.
 7. The image forming apparatus as claimed in claim 2, wherein thethickness coefficient is calculated using the following equation:$K_{thickness} = {\frac{{amount}\mspace{14mu} {of}\mspace{14mu} {transmitted}\mspace{14mu} {light}}{{{amount}\mspace{14mu} {of}\mspace{14mu} {diffuse}} - {{reflected}\mspace{14mu} {light}^{k\; m}}} + {{Ka}^{*}\left( {\frac{{{amount}\mspace{14mu} {of}\mspace{14mu} {regular}} - {{reflected}\mspace{14mu} {light}}}{{{amount}\mspace{14mu} {of}\mspace{14mu} {diffuse}} - {{reflected}\mspace{14mu} {light}}} - 1} \right)}}$where the coefficient K_(thickness) denotes the thickness coefficient,km denotes a conveyance path width calibration coefficient determinedaccording to a distance between any one of light receiving sensorsdetecting an amount of the regular reflected light, an amount of thediffused reflected light, and the amount of the transmitted light and alight emitting element, and ka denotes an initial calibrationcoefficient determined according to emission characteristics of thelight emitting element.
 8. The image forming apparatus as claimed inclaim 2, wherein the processor is to determine an error when an outputvalue of any one of light receiving sensors detecting the amount of thefirst reflected light, the amount of the second reflected light, and theamount of the transmitted light is changed based on a change in theamount of emitted light from a light emitting element and a proportionof the change in the output value to a predetermined reference lightemission amount exceeds a predetermined upper limit value.
 9. The imageforming apparatus as claimed in claim 1, wherein the sensor includes: alight emitting device including at least one light emitting element; afirst light receiving sensor to sense the amount of light transmittedthrough the printing medium among light irradiated from the at least onelight emitting element; a second light receiving sensor to detect anamount of light regular reflected from the printing medium among lightirradiated from the at least one light emitting element; and a thirdlight receiving sensor to detect an amount of the reflected lightdiffuse reflected from the printing medium among light irradiated fromthe at least one light emitting element.
 10. The image forming apparatusas claimed in claim 1, wherein the sensor includes a light receivingsensor rotating in a measurement plane including an optical axis of alight emitting element perpendicular to the printing medium based on ameasurement point which is an intersection point of the optical axis andthe printing medium, and the light receiving sensor is to measure theamount of the transmitted light at a regular transmission angle, measurean amount of the regular reflected light at a regular reflection angle,and measure an amount of the diffused reflected light at a diffusereflection angle.
 11. The image forming apparatus as claimed in claim 2,wherein the sensor includes a first light receiving sensor and a secondlight receiving sensor rotatable in a measurement plane including anoptical axis of a light emitting element perpendicular to the printingmedium based on a measurement point which is an intersection point ofthe optical axis of the light emitting element and the printing medium,the first light receiving sensor is to measure the amount of thetransmitted light at a regular transmission angle, and the second lightreceiving sensor is to measure the amount of the regular reflected lightat a regular reflection angle and measure the amount of the diffusedreflected light at a diffuse reflection angle.
 12. An image formingmethod of an image forming apparatus, the image forming methodcomprising: irradiating light to a printing medium; detecting an amountof light transmitted through the printing medium; detecting an amount oflight reflected from the printing medium to each of a plurality ofpositions; determining a thickness of the printing medium based on theamount of light transmitted through the printing medium and the amountof light reflected to the printing medium at each of the plurality ofpositions; and forming an image on the printing medium based on thedetermined thickness.
 13. The image forming method as claimed in claim12, wherein, the determining comprises calculating an amount ofcalibrated transmitted light by normalizing the amount of thetransmitted light through the printing medium based on an amount of afirst reflected light among the light reflected from the plurality ofpositions; calculating an amount of calibrated reflected light bynormalizing amount of a second reflected light different from the amountof the first reflected light based on the amount of the first reflectedlight; calculating a thickness coefficient by adding the amount of thecalibrated transmitted light and the amount of the calibrated reflectedlight; and determining the thickness of the printing medium based on thecalculated thickness coefficient, wherein the amount of the firstreflected light is an amount of diffused reflected light, and whereinthe amount of the second reflected light is an amount of regularreflected light.
 14. The image forming method as claimed in claim 13,further comprising: storing a calibration table in which initialcalibration coefficients according to emission characteristics of alight emitting element irradiating light to the printing medium arematched in advance, wherein, the calculating the amount of thecalibrated reflected light comprises, calculating the amount of thecalibrated reflected light based on a value obtained by normalizing theamount of the second reflected light based on the amount of the firstreflected light and the initial calibration coefficient.
 15. The imageforming method as claimed in claim 13, further comprising: storing acalibration table in which conveyance path width calibrationcoefficients according to distances between a light receiving sensordetecting any one of the amount of the transmitted light, the amount ofthe regular reflected light, and the amount of the diffused reflectedlight and a light emitting element are matched in advance, wherein, thecalculating the amount of the calibrated transmitted light comprisesdetermining a conveyance path width calibration coefficient based on thedistance between the light receiving sensor and the light emittingelement, and calculating the amount of the calibrated transmitted lightby normalizing the amount of the transmitted light based on theconveyance path width calibration coefficient and the amount of thefirst reflected light.